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An insurance premium audit trues up the estimated payroll and receipts on your policy against the real numbers after the term ends. Both general liability and workers comp run this reconciliation, which is why that 'additional premium' bill is a catch-up, not a penalty. HVAC companies owe more for three specific reasons.
A busy summer install season pushes payroll past the lean estimate you gave at renewal. Subcontractors who cannot show a certificate of insurance get charged to your payroll as employees. And techs whose time is not documented land in the highest-rated class. This guide covers how the workers comp audit works, what the auditor wants, and how to dispute a bill that is wrong.
You owe more because your premium started as an estimate, and the audit charges you for what actually happened. General liability and workers comp both price off projected payroll and receipts at renewal. When your real payroll, revenue, or crew size comes in higher, the audit bills the difference.
Premium equals a rate times an exposure base, and that base (payroll for workers comp, payroll and gross receipts for general liability) is a forecast, per IRMI. Because it is a forecast, the year-end audit almost always changes the number, up or down. For an HVAC shop, seasonality does the damage. You price the policy on a spring crew, staff up through summer, and the audit invoice lands months later. A claim-free year still ends with a catch-up bill. Readers who want the full renewal picture can start with the HVAC insurance program guide and the coverage detail on HVAC insurance.
After the policy term ends, the carrier audits your actual exposure one of three ways: a self-report form (now usually an online portal), a virtual audit with records emailed over, or a physical on-site review of your books. Workers comp verifies payroll. General liability verifies payroll and gross receipts.
The methods differ mainly in how much of your paperwork the auditor touches, but any one pass can settle both general liability and workers comp at once. Timing surprises people. The audit runs after the term expires, and carriers generally have up to three years after expiration to complete it, though California limits it to one year. Keep payroll, tax, and subcontractor records at least that long. If you added trucks or crew mid-year, it helps to endorse new techs and vans mid-term so the change is on record before the audit finds it.
A premium auditor wants the records that prove your actual payroll and who you paid. Expect to hand over payroll registers, federal Forms 940 and 941, state unemployment returns, W-2s and 1099s, the general ledger, job-cost records, overtime records, and a certificate of insurance for every subcontractor.
The State Fund of California audit guide lists what a premium auditor pulls:
Thin records cost you. Without specific time records, the auditor can assign an employee's entire payroll to the highest-rated classification that touches any part of the work, and the payroll cannot be split by percentages, averages, or estimates, per WCIRB Rule 3. How your payroll gets classified is the whole game, which is why HVAC workers comp class codes decide what you owe.
Collect a valid certificate of insurance from every subcontractor before they start, plus a license where your state requires one. A sub who cannot prove their own workers comp at the audit gets treated as your employee, and what you paid them is added to your payroll at your rate. A 1099 does not change that.
This is the single biggest surprise-bill driver, and the misconception behind it is simple: a 1099 is a tax form, not proof of coverage. When a subcontractor cannot produce a certificate at audit and has no valid license, the money you paid them may be counted as payroll, per State Fund. The general liability side does the same thing when a sub carries no coverage of its own. The fix is a habit. Check the coverage type (workers comp, not just general liability), check the dates, and file the certificate before the crew starts. The deeper mechanics live in our breakdown of when your comp audit picks up uninsured subcontractor payroll.
Yes. Two HVAC-specific mechanics quietly raise the bill. If you cannot show which payroll was install work versus service work, the auditor can push all of it into the higher-rated class. And overtime gets special treatment: in most states the overtime premium portion comes out before workers comp premium is charged.
HVAC work rates under class code 5537, which bundles installation, service, and repair together, while standalone sheet-metal work is classified separately. Splitting install from service payroll needs real timesheets, or Rule 3 sends everything to the higher rate.
Overtime is the rule no competitor covers. In most states, the extra premium on overtime wages is excluded from workers comp payroll: roughly one-third of time-and-a-half pay and half of double-time. Picture a tech earning $30 an hour who works summer overtime at $45. The $15 premium portion gets stripped before premium applies, so unseparated overtime means paying comp on wages you did not owe. A few states count full overtime, so verify yours. The step-by-step sits in documenting installer vs service-tech payroll splits at audit.
Prepare all year, not the week the auditor calls. Keep payroll estimates current, separate overtime and installer-versus-service time on the timesheets, and collect a certificate of insurance from every sub before work starts. When the audit arrives, hand over clean records. If the bill still looks wrong, dispute it in writing.
A short pre-audit checklist keeps the number honest:
If the bill is wrong, you have a real dispute path, not just an angry phone call. Request a copy of the completed audit worksheet, then submit a written dispute that names each disputed item with corrected records attached. The State Fund audit guide is clear that vague or verbal complaints are not treated as an official dispute. If the carrier will not fix a plain error, escalate to your state insurance department.
A flat-fee broker like Coverwatch preps clients for the audit and challenges a bill that charged uninsured-sub payroll or the wrong class code, because a flat fee carries no commission tied to a higher premium. Smoothing seasonal swings helps too, and pay-as-you-go workers comp reports payroll as you run it so the year-end true-up shrinks. The audit is won in the records you keep between renewals, not the week the auditor emails. Coverwatch runs that review for HVAC clients as part of its flat-fee contractor insurance practice: certificate tracking, class-code and overtime checks, and a dispute when the number is wrong.
Only when they cannot prove their own coverage. A sub who produces a valid workers comp certificate of insurance, and a license where the state requires one, stays off your payroll. A sub who cannot is treated as your employee at the audit, and what you paid them is charged as payroll at your rate. A 1099 does not change that outcome.
Because your premium was based on an estimate, not on your claims. The audit compares the payroll and receipts you projected at renewal against the real numbers. If payroll grew over the summer, revenue rose, or subs went uncertificated, you owe the difference. Claims history affects your future rate, not this year-end reconciliation.
Yes. Request a copy of the completed audit worksheet, then submit a written, specific dispute with corrected records covering every item you contest. Vague or verbal complaints are not treated as an official dispute. If the carrier does not fix a clear error, you can escalate to your state insurance department.
Pull payroll registers, Forms 940 and 941, state unemployment returns, W-2s and 1099s, the general ledger, and job-cost records. Separate overtime and split installer versus service time on the timesheets. Keep a certificate of insurance on file for every subcontractor. Clean records hold your techs in the right class codes and keep the bill honest.
Carriers generally have up to three years after the policy expires to conduct the audit, though California limits it to one year. Keep payroll, tax, and subcontractor certificate records at least that long so you can support the numbers or dispute them if the audit is wrong.
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